This invention relates to active transmitter circuits for radar systems.
Radar or communications systems including an active transmitter module coupled to a passive array antenna or sub-array could benefit with an efficient feed network that enables solid state combining. Generic solid state devices have been shown to be more functional, reliable, compact, easily upgraded and lower cost compared to the maintenance of tube based systems.
However, considerations including ohmic feed losses, size and costs have discouraged replacing vacuum tube systems with high power solid state systems at microwave frequencies. In particular, high power solid state microwave systems built with poor efficiency increases solid state device counts which resulted in increased size and cost. The new technique for combining solid state devices as disclosed herein achieves cost and size competitiveness and offers improved performance compared to vacuum tube systems.
Low loss waveguide corporate combining has advantages, assuming volume is available. The drawback of the corporate waveguide feed is that for 2N modules typically there need to be N levels of combining. The design for a radial combiner can be difficult in terms of impedance match, and also the orientation may not lend itself adaptable for cooling modules. A series resonant combiner, although very efficient and compact, works best only when all modules are functional and over very narrow bandwidths. A drawback for prior attempts using traveling wave feeds has been that a larger number of ports (e.g., up to 50) usually have been necessary for better efficiency. Combining solid state devices is more manageable if done in smaller subarray groups. Design, manufacturing and maintenance of solid state subarray power blocks is sometimes difficult to achieve using state of the art combining techniques.
There is accordingly a need a reliable, compact and efficient solid state amplifier microwave combiner.
A solid state transmitter circuit is described that includes a divider series feed signal line, a collector series feed signal line, a plurality of parallel solid state amplifier coupler circuits connected between the divider series feed line and the collector series feed line, and phase shifting circuitry distributed along the divider series feed line for compensating phase tracking error between the divider series feed line and the collector series feed line. A further aspect is a signal injection circuit connected between an input of the divider series feed line and an input of the collector series feed line.